1. Field of the Invention
The present invention relates particularly to a recording liquid suited to ink-jet recording method that makes a record by flying a recording liquid from an orifice of a recording head by the action of heat energy.
2. Related Background Art
Ink-jet recording systems are advantageous in that they make less noise at the time of recording, can be readily matched to color recording, and also can obtain a recorded image with a high resolution at a high speed using a highly integrated head.
In ink-jet recording systems, liquids used as ink are those comprising various water-soluble dyes dissolved in water or in a mixed solution of water and an organic solvent. When, however, the water-suluble dyes are used, the light-resistance of recorded images is often questioned because of these water-soluble dyes, which have a poor light-resistance by nature.
The water resistance is also often questioned because of the dye, which is water-soluble. More specifically, when recording images are wetted with rain, sweat, or water used for drinking or food, the recorded images may sometimes blur or disappear.
On the other hand, similar problems may also arise in writing materials such as ball-point pens, in which dyes are used. In order to solve such problems of light-resistance and water resistance, various water-based pigment inks used for writing materials have been proposed. For the purpose of putting the water-based pigment inks into practical use, it has been studied to assure their dispersion stability, prevention of ink from solidifying at pen points, and prevention of balls of the ball-point pens from wearing.
For example, Japanese Patent Application Laid-Open No. 61-246271 discloses an ink composition used for writing implements, which has improved dispersion stability and drying resistance by the use of a water-soluble amine salt, ammonium salt or metal salt of a copolymer composed of a hydrophilic addition-polymerizable monomer as a water-soluble resin and a styrene and/or styrene derivative monomer. Japanese Patent Application Laid-Open No. 62-72774 discloses a water-based pigment ink used for ball-point pens which is free from the ejection-down phenomenon and the ink-off phenomenon by the use of polysiloxane.
These, however, have had the disadvantage that they cause serious difficulties in ejection stability when used in ink-jet recording systems that record by propelling the conventional water-based pigment ink used for writing materials from an orifice of a recording head by the action of heat energy.
Some of the conventional water-based pigment inks can exhibit excellent ejection performance in their ejection for a relatively short time, but cause the problem that the ejection becomes unstable and no ejection may result at length when the driving conditions of a recording head are varied or ink is continuously ejected for a long period of time.